the power to protect
high RESISTANCE
GROUNDING systems
the power to protect
Product Guide
D, Eaton Cutler-Hammer, Siemens,
Cooper Power
Hi-Tech - Intel, Research in Motion,
IBM Data Centre, Honeywell
Aerospace
Ground Fault Protection
1
Neutral Grounding Resistors
2
High Resistance Grounding
6
Stoplight
8
Sleuth
10
Gemini
12
Sentinel System
14
Fusion
18
Comparative Performance
Rating
Process Industries - Dofasco,
Nestle, Johnson & Johnson, Labatts,
Proctor and Gamble, Bayer
Consultants - SNC Lavalin, CoSyn,
Fluor Daniel, Bechtel, Bantrel,
Stantec, Hatch
MINING & automotive - Inco,
Petro-chemical - Shell, Petro-
Newmont, Falconbridge, General
Motors, Magna, Narmco, Keiper
Table of Contents
Canada, Exxon-Mobil, Dow
Chemical, Syncrude, Imperial Oil
Municipal / Commercial - Royal
20
the power to protect
OEM’s - General Electric, Square
Bank, Pearson Airport, Department of
Defense, Leamington Hospital
Potential ground faults often go unnoticed and can cause havoc on plant
production processes. Shutting down power and equipment, ground faults
disrupt the flow of products through manufacturing processes, leading to
hours or even days of lost productivity.
Undetected ground faults can also pose potential health and safety risks
to personnel. Ground faults can lead to safety hazards such as equipment
malfunctions, fire and electric shock.
Ground faults can cause serious damage to equipment and to your processes.
During a fault condition, equipment can be damaged and processes shut
down, seriously affecting your bottom line.
The concern for ground fault protection is
based on four factors:
1
2
3
4
The majority of electrical faults include ground.
The ground fault protective sensitivity can be relatively
independent of continuous load current values and thereby
have lower pickup settings than phase protective devices.
Since ground fault current are not transferred through system
power transformers… the ground fault protection for each
system voltage level is independent… This permits faster
relaying that can be afforded by phase protective devices.
Arcing ground faults that are not properly detected and cleared
can be extremely destructive.
With 25 years industry experience combined with technical leadership and
investment in new and innovative products, I-Gard has the Power to Protect.
We offer a full range of neutral grounding resistors for low resistor
grounding systems and the industry’s widest range of high resistor
grounding systems.
1
ngr
NEUTRAL GROUNDING
Resistors
I-Gard offers a complete range of Neutral Grounding Resistors from
480V to 69,000 volts and utility for resistance grounding of industrial
power systems and are connected between earth ground and the
neutral of power transformers, power generators or artificial neutral
transformers.
Neutral Grounding Resistors are similar to fuses in that they do
nothing until something in the system goes wrong. Then, like fuses,
they protect personnel and equipment from damage. Damage comes
from two factors, how long the fault lasts and the fault magnitude.
Ground fault relays trip breakers and limit how long a fault lasts based
on current. Neutral grounding resistors limit the fault magnitude.
The I-Gard Neutral Grounding Resistor with integral
Sigma Relay is the only NGR that controls both factors.
Neutral Grounding resistors limit the
maximum fault current to a value which will
not damage generating, distribution or other
associated equipment in the power system,
yet allow sufficient flow of fault current to
operate protective relays to clear the fault.
The I-Gard SIGMA MONITOR RELAY is a
combination Neutral Grounding Resistor
(NGR) monitor and Ground Fault relay. In
distribution systems employing Resistance
Grounding the SIGMA MONITOR RELAY
protects against ground faults and abnormal
conditions in the path between system
neutral and ground possibly caused by loose
or improper connections, corrosion, foreign
objects or missing or compromised copper
ground wires.
The SIGMA MONITOR RELAY measures
the current through the NGR, the transformer
neutral-to-ground voltage and the NGR
resistance. The relay compares the measured
values against the field settings of the
relay and provides relay outputs and LED
indications when an abnormal condition
is detected.
2
Why the I-Gard NGR is different:
The only NGR with integral monitoring of
grounding circuit (2400v and above models)
The only NGR with integral ground fault
relay(2400v and above models)
Designed with special element material with
low temperature coefficient of resistivity
for consistent fault current levels
Edgewound element design eliminates hot-spots
CSA certified and UL approved
Why consider low resistance grounded
over solidly grounded?
While solidly grounded systems are an improvement over ungrounded systems,
and speed the location of faults, they lack the current limiting ability of resistance
grounding and the extra protection this provides. The destructive nature of arcing
ground faults in solidly grounded systems is well known and documented by IEEE and
are caused by the energy dissipated in the fault.
A measure of this energy can be obtained from the estimate of Kilowatt-cycles
dissipated in the arc: Kilowatt cycles = V x I x Time (cycles) /1000
100 Kilowatt CyclesFault location identifiable at close inspection-spit
marks on metal and some smoke marks
2000 Kilowatt CyclesEquipment can usually be restored by painting
smoke marks and repairing punctures in insulation
6000 Kilowatt CyclesMinimal amount of damage, but fault more easily located
10,000 Kilowatt Cycles
Fault probably contained by the metal enclosure
20,000 Kilowatt CyclesFault probably burns through single thickness
enclosure and spreads to other sections
Over 20,000 Kilowatt Cycles Considerable destruction
There are two broad categories of resistance grounding: low resistance and high
resistance. In both types of grounding, the resistor is connected between the neutral
of the transformer secondary and the earth ground and is sized to ensure that the
ground fault current limit is greater than the system’s total capacitance-to-ground
charging current.
Low resistance grounding of the neutral limits the fault current to a high level
(typically 50 amps or more) in order to operate protective fault clearing relays.
These devices are then able to quickly clear the fault, usually within a few seconds.
What does IEEE say about Low Resistance Grounding?
IEEE Std 142-1991 Recommended Practice for Grounding
of Industrial and Commercial Power Systems
Clause 1.4.3 Resistance Grounding
The low-resistance method has the advantage of immediate and selective
clearing of the grounded circuit, but requires that the minimum ground-fault
current be large enough to positively actuate the applied ground-fault relay
IEEE Std 242-1986 Recommended Practice for the Protection and
Coordination of Industrial and Commercial Power Systems
Clause 7.2.3 Low-Resistance Grounding
The magnitude of the grounding resistance is selected to allow sufficient
current for ground-fault relays to detect and clear the faulted circuit
Comparison of Damage
2000 kvA, 480 Volt system, single phase fault current available 30,000 amps
Solidly Grounded Assumes breaker opens in 10 cycles or 0.16 seconds
100 x 30,000 x 10 / 1000 = 30,000 KWC
Low Resistance Grounded, 50 Amps 1 second
100 x 50 x 60 / 1000 = 300 KWC
3
The key reasons for limiting the fault current through resistance grounding are:
To reduce burning / melting effects in faulted electrical equipment, such as switchgear, transformers,
cables and rotating machines
To reduce mechanical stresses in circuits and apparatus carrying fault currents
To reduce electric shock hazards to personnel caused by stray ground fault currents
in the ground return path
To reduce arc blast or flash hazard to personnel who may have accidentally caused or who happen
to be in close proximity to the fault current
To secure control of transient over voltages
All I-Gard’s low resistance grounding products are standardized on the edgewound element
design. Because of the rapid heating and very high temperatures encountered, this design
has been proven superior for the NGR application.
The edgewound element material is mounted on porcelain supports, which are not affected
by the high temperature or high voltages. The sturdy, helically coiled element is free to
expand and does not deform when heated and offers consistent current density.
The element material is critical in ensuring high operating performance of the neutral
grounding resistor. The element material is a special grade of electrical alloy with a
low temperature coefficient of resistance. This prevents the resistance value from
increasing significantly as the resistor operates through a wide temperature range.
It also ensures a stable value of the fault current for proper metering and relaying.
Some manufacturers offer stamped and cast alloy grids resistors for low resistance
grounding applications but the mica paper insulation they incorporate limits the temperature
at which they can operate. The mica paper insulation can also absorb moisture and fail
while the flat grid stampings may severely warp when rapidly heated. Also, the grids have
hot spots which may burn when overloaded by the fault.
To ensure sufficient fault current is available to positively actuate
the over-current relay and that the fault current does not decrease by
more than 20% between ambient and the full operating temperature, it
is recommended that the NGR element material to be specified to have
a temperature coefficient not greater than 0.0002 ohms / C.
Typical NGR 8000 Volts, 1000 Amps 10 seconds, 760 C temperature rise as per IEEE 32.
4
Material 1
AISI 304 Nickel Chrome
Competitor 1
Material 2 AISI 430
Competitor 2
Material 3
Aluminum Chrome
Steel 1JR (Ohmalloy)
Temp Coefficient
of Resistance
0.001 ohms / C
0.00135 ohms / C 0.00012 ohms / C
Ohms at Ambient 8000 / 1000 = 8 ohms
8000 / 1000 = 8 ohms 8000 / 1000 = 8 ohms
After 10 Seconds 8 * (1+0.001 * 760) = 14.08 ohms
8 * (1+0.00135 * 760) = 16.21 ohms 8 * (1+0.00012*760) = 8.7 ohms
Operating Fault
Current
8000 / 14.08 = 568 amps
8000 / 16.21 = 493 amps 8000 / 8.7 = 919 amps
Change
43.2%
50.7% 8.1%
SIGMA
Technical Specifications
Electrical Ratings
Control Power:
Maximum:
Output Relay Contacts
110-240V AC/DC
Main Trip Relay: (60-264V AC/DC)
Type: Form Z (NO and NC pair)
Auxiliary Ground Fault Relay: Type:
1 Form C (NO/NC)
Rating: 10A@240Vac, 8A@24Vdc, 1/2HP@240Vac
Auxiliary NGR Fault Relay:Type:
-45% to +10%
5VAac or 5Wdc
Rating: 10A@240Vac, 10A@30Vdc, 1/2HP@240Vac
50/60Hz
1 Form C (NO/NC)
Rating: 10A@240Vac, 8A@24Vdc, 1/2HP@240Vac
Electrical Tests
Surge test:@ 3kV
Dielectric test: @ 2kV for 1 minute
Temperature Range Operating: -40˚C to +60˚C
Storage:-50˚C to +70˚C
Physical Dimensions:
Length: 157mm (6.18 in.)
Width:
Height:
Weight: 344g
58 mm (2.28 in.)
86mm (3.39 in.)
Ground Fault Circuit CT Input: Non-Isolated. One side of the CT input, terminal 22, is internally grounded.
CT Ratio: T2A, T3A or equivalent
DIP Switch Settings Trip Level:8 settings: 5%, 10%, 15%, 20%, 25%, 30%, 40%, and 50% of the set
NGR Current Setting
Trip Time: 32 settings, 0-60 msec.,
150 msec. to 3.15 sec. in 100 msec. steps
Accuracy:
Repeat: ±1%
Trip Current: ±10%
Meter Output: ±2% at full scale.
Thermal Characteristics:
Short Time Withstand 400A for 1 sec.
65287
Trip Time:±10%, ±10 msec.
E222372
5
high resistance grounding
High resistance grounding provides the same
voltages associated with ungrounded systems.
advantages as ungrounded systems yet limits
There is no arc flash hazard as there is with solidly
the steady state and severe transient over-
grounded systems.
IEEE Std 141-1993
Stoplight
Sleuth
Current limiting resistor
Current limiting resistor
Integral ground fault relay
Integral ground fault relay
Fault location through pulsing
Basic
Harmonic filter and time / current
adjustments to reduce false trips
Industry Standard
Safety through Innovation
6
At I-Gard we have the necessary high
and application research, I-Gard leads the way
resistance grounding products to cover all
in bringing innovative new products to market
applications. With significant expenditure
with a commitment to reducing electrical
dedicated annually to product development
hazards.
For low voltage power distribution systems, high
is proven effective in significantly reducing the
resistance grounding enhances reliability and
frequency and severity of arc flash accidents.
uptime of power distribution equipment and
Gemini
Sentinel
Dual path current limiting resistor
Current limiting resistor
Redundant fail-safe resistor circuit
Voltage and current sensing
Integral ground fault relay
Integral ground fault relay
Integral ground monitoring relay
Integral ground monitoring relay
Fault location through pulsing
Fault location through pulsing
Harmonic filter and time / current
adjustments to reduce false trips
Harmonic filter and time / current
adjustments to reduce false trips
2003 IEEE IAS Safety Workshop
Inrush detection restraint
Premium
Modular and scalable
Multi-feeder protection
Second fault protection
MODBUS for remote monitoring
Ultra Premium
7
STOPLIGHT
STOPLIGHT is a complete, inexpensive high resistance grounding
system that provides system wide protection against damaging
ground faults. Using a simple but effective three light system, Stoplight
provides visual indication and available remote annunciation to inform
operations and maintenance personnel of ground faults.
A red light indicates an active ground fault, an amber light indicates
a ground fault has occurred but is intermittent and a green light signifies
that there are no active ground faults on the system.
Ground faults cause havoc on plant
production processes, shutting down
power and equipment and critical loads.
Ground faults disrupt the flow of
products through manufacturing
processes and cause data loss in
computer centers leading to hours
or even days of lost productivity.
Ground faults pose potential
health and safety risks to personnel,
creating hazards such as equipment
malfunctions, fire and electric shock.
High Resistance Grounding (HRG) is
becoming more prevalent in industrial
and commercial electrical power
systems because it eliminates unscheduled downtime due to ground
faults, and improves personnel safety by
preventing ground faults from escalating
into arc-flash incidents. Resistance
Grounding
is highly recommended for generators,
to protect them from damage due to
excessive ground fault currents.
8
Inexpensive ground fault protection with
visual indication in NEMA 3R enclosure
Optional pulsing system for easier fault location
Unique 3 light system for easy visual
indication of system condition
Available for 480V, 600V and 4160V
distribution systems
The four key integrated elements
To System Neutral
No. 8 AWG Min.
contained in the Stoplight system
0-5A
work to protect against damaging
ground fault currents.
0-500V
A
G
R
V
Y
To System Ground
No. 8 AWG Min.
Schematic shows
optional pulsing
1. High Resistance Grounding Resistor
This resistor is connected to the wye
generator supplying the facility. Its function
to non-damaging levels under a single
This provides the user an opportunity to
to detect and clear the fault.
point of the transformer or
is to limit ground fault currents
line-to-ground fault condition.
retain process continuity and
2. Ground Fault Sensing Transformer and Relay
This microprocessor based digital relay measures ground fault current
using a 1:1 zero sequence current transformer. It maintains accuracy
over a range of 45Hz to 65Hz and filters out harmonics to eliminate
nuisance tripping.
3. Automatic Pulsing System (optional)
Once the pulsing feature on the STOPLIGHT system is selected and
activated, the system will cyclically limit the fault to 100%, 75% and 50%
of the available ground fault current. The cyclical pulsing combined with the
hand held pulse tracing sensor empowers the user to trace the fault circuit
to the point of the fault even in complex distribution systems without
de-energizing the load.
4. Hand Held Pulse Tracing Sensor (for use with optional pulsing system)
This device, similar to a clamp-on ammeter, allows the user to follow the
pulses from their source at the STOPLIGHT unit through to the specific
location of the line to ground fault. Once the fault is located, it can be isolated
and repaired.
65287
E222372
9
sleuth
SLEUTH
SLEUTH is a neutral grounding device that limits ground fault currents
to non-damaging levels under a single line-to-ground fault condition.
SLEUTH is the ideal tool for sensing and locating ground faults
quickly and easily. When a ground fault occurs, SLEUTH controls
and limits the fault current, provides an alarm that indicates an active
fault, enabling electrical personnel to follow a simple sequence to
locate and isolate the fault without interrupting the circuit or opening
circuit breakers.
Ground faults cause havoc on plant
production processes, shutting down
power and equipment and critical loads.
Ground faults disrupt the flow of
products through manufacturing
processes land cause data loss in
computer centers leading to hours or
even days of lost productivity.
Ground faults pose potential health
and safety risks to personnel, creating
hazards such as equipment malfunctions,
fire and electric shock.
High Resistance-Grounding (HRG) is
becoming more prevalent in industrial
and commercial electrical power systems
because it eliminates unscheduled
downtime due to ground faults, and
improves personnel safety by preventing
ground faults from escalating into arcflash incidents. Resistance Grounding
is highly recommended for generators,
to protect them from damage due to
excessive ground fault currents.
10
NEMA 3R enclosure containing current
limiting resistor and ground fault relay
Available with artificial neutral for use on
delta systems
Visual indication of system normal, active
ground fault and pulsing active
Available for 480V, 600V and 4160V
distribution systems
The first step in protection is to limit
damaging fault currents through the
To System Neutral
No. 8 AWG Min.
use of a High Resistance Grounding
system.
The next step requires the fault to
be located and repaired before a
V
0-500V
A
0-5A
GF
second fault occurs.
Ground Fault
Relay
The Sleuth pulsing system contains
four key integrated elements that limit
damaging fault currents and provide
process continuity. Also, the integral
pulsing system facilitates the locating
Ground Fault
Active
G
System Healthy
R
Ground Fault
Active
F
Pulsing On
To System Ground
No. 8 AWG Min.
of the ground fault in the shortest time,
so the operator is able to schedule the
isolation and correction of the fault at
a convenient time.
1. High Resistance Grounding Resistor
This resistor is connected to the wye
generator supplying the facility. Its function
to non-damaging levels under a single
This provides the user an opportunity to
to detect and clear the fault.
point of the transformer or
is to limit ground fault currents
line-to-ground fault condition.
retain process continuity and
2. Hand Held Pulse Tracing Sensor
This device, similar to a clamp-on ammeter, allows the user to follow the pulses
from their source at the SLEUTH unit through to the specific location of the
line to ground fault. Once the fault is located, it can be isolated and repaired.
3. Automatic Pulsing System
Once the pulsing feature on the SLEUTH system is selected and activated,
the system will cyclically limit the fault to 100%, 75% and 50% of the
available ground fault current. The cyclical pulsing combined with the
hand held pulse tracing sensor empowers the user to trace the fault circuit
to the point of the fault in even in complex distribution systems without
de-energizing the load.
4. Ground Fault Sensing Transformer and Relay
This microprocessor based digital relay measures ground fault current
using a 1:1 zero sequence current transformer. It maintains accuracy
over a range of 45Hz to 65Hz and filters out harmonics to eliminate
nuisance tripping.
65287
E222372
11
GEMINI
GEMINI is a unique patented, fail safe, all-in-one neutral grounding
system that combines ground fault protection with a redundant resistor
system, in addition to a built-in resistor integrity monitoring relay.
Providing protection against any compromising of the resistor integrity,
the patented twin resistance paths in combination with the integrity
monitoring relay form the heart of the Gemini system. Limiting any
ground fault to predetermined and safe levels, the parallel resistance
circuit protects against the damaging effect of a ground fault. Should
the integrity of either resistor path be compromised, the second
path continues to provide the necessary protection while an alarm
is activated.
Ground faults cause havoc on plant
production processes, shutting down
power and equipment and critical loads.
Ground faults disrupt the flow of
products through manufacturing
processes and cause data loss in
computer centers leading to hours
or even days of lost productivity.
Ground faults pose potential health and
safety risks to personnel, creating hazards
such as equipment malfunctions, fire and
electric shock.
High Resistance Grounding (HRG) is
becoming more prevalent in industrial
and commercial electrical power systems
because it eliminates unscheduled
downtime due to ground faults, and
improves personnel safety by preventing
ground faults from escalating into arc-flash
incidents. Resistance Grounding
is highly recommended for generators,
to protect them from damage due to
excessive ground fault currents.
12
Patented fail-safe high resistance grounding
system with twin resistance paths
Only monitoring relay capable of
discriminating between ground faults, resistor
failure and open and short circuits
Eliminates nuisance tripping through adjustable
time delay settings 60 milliseconds up
Self diagnosis through built-in test circuitry
The GEMINI system contains a high
resistance grounding unit, a ground
fault relay and a resistor integrity
monitor. It is available with optional
pulsing capability for easier fault
location.
1. High Resistance Grounding System
This resistor is connected to the wye point of the transformer or
generator supplying the facility. Its function is to limit ground fault currents
to non-damaging levels under a single line-to-ground fault condition.
In the case of the GEMINI system there is a parallel resistance circuit
comprised of two identical resistor paths connected from the neutral to
the ground. The parallel resistance circuit is sized to limit any ground fault
to predetermined levels. In the unlikely event that one resistor path fails,
the second resistor path continues to limit the ground fault to half of the
predetermined levels and still provides full ground fault protection and an
alarm indicating resistor failure.
2. Ground Fault and Resistor Integrity Relay (GFR-RM)
In conjunction with a sensing resistor and a series current transformer,
the GFR-RM measures current through the neutral grounding resistor,
transformer neutral to ground voltage and NGR resistance for continuity. The
GFR-RM compares the measured values against the field settings of relay
and provides relay outputs and lighted signal when an abnormal condition
is detected.
The GFR-RM is the only relay with the capability to discriminate between
ground faults, resistor failure and open and short circuits. The unit trips in
1.5 seconds when NGR failure is detected. NGR failure is determined when
resistance varies to less than 66% or more than 150% of the selected value.
3. Automatic Pulsing System (optional)
Once the pulsing feature on the GEMINI system is selected and activated, the
system will cyclically limit the fault to 100%, 75% and 50% of the available
ground fault current. The cyclical pulsing combined with the hand held pulse
tracing sensor empowers the user to trace the fault circuit to the point of the
fault in even in complex distribution systems without de-energizing the load.
65287
E222372
13
sentinel
SENTINEL SYSTEM
The Sentinel is the industry’s most advanced high resistance
grounding system. It is designed to protect your continuous process or
critical power system from unnecessary outages of electrical power.
The Sentinel detects the event of a single ground fault, signals an
alarm, and points to the affected branch or feeder. Thus maintenance
can be immediately alerted to the problem and an operator dispatched
to locate the fault to isolate it promptly.
Ground faults cause havoc on plant
production processes, shutting down
power and equipment and critical loads.
Ground faults disrupt the flow of
products through manufacturing
processes and cause data loss in
computer centers leading to hours
or even days of lost productivity.
Ground faults pose potential health
and safety risks to personnel, creating
hazards such as equipment malfunctions,
fire and electric shock.
High Resistance-Grounding (HRG) is
becoming more prevalent in industrial
and commercial electrical power systems
because it eliminates unscheduled
downtime due to ground faults, and
improves personnel safety by preventing
ground faults from escalating into arcflash incidents. Resistance Grounding
is highly recommended for generators,
to protect them from damage due to
excessive ground fault currents.
NEMA 3R enclosure containing current limiting
resistor and ground fault relay and isolation switch
Phase and feeder indication resulting in quicker
fault location
Monitors and protects up to 50 feeders on one relay
Available first fault alarm, first fault trip or first
fault time delay trip
Integral resistor monitoring module eliminates
requirement for separate monitoring relay
Unique selective instantaneous feeder trip (sift)
on occurrence of second ground fault
14
Additional Safety Features
1
2
Phase Indication
NGR
NGR
DSP HRG
Feeder Identification
ZSCS
DSP HRG
...Several Feeders...
Motor
3
ZSCS
...Several Feeders...
Motor
Motor
Motor
Faulted Feeder Options
Options for Faulted Feeder:
Alarm Only (No Trip) or
Trip with Time Delay
TRIP
NGR
DSP HRG
ZSCS
ZSCS
...Several Feeders...
Motor
4
Motor
Selective Second Ground Fault Protection
2nd Ground Fault:
Prioritize Feeders
Trips least important,
maintaining operation on
most important
Up to 50 Feeders
TRIP
NGR
DSP HRG
ZSCS
ZSCS
...Several Feeders...
Motor
Motor
15
Additional Safety Features
5
Open/Short Protection
System Ground Monitor:
Continually monitors circuit
from Neutral to Ground
TRIP
NGR
ZSCS
DSP HRG
ZSCS
Alarms if OPEN circuit
Alarms if SHORT circuit
...Several Feeders...
DSP-DRM
Complies with M421
Motor
Motor
6
Main-Tie-Main Applications
Cable adapter CA(S):
Controlled by tie breaker contact
TRIP
TRIP
ZSCS
DSP HRG
NGR
ZSCS
ZSCS
...Several Feeders...
Motor
Allows coordination of two
systems either separately (Tie
open) or combined (Tie closed)
Motor
ZSCS
DSP HRG
...Several Feeders...
Motor
Motor
DSP-CA
DSP-CAS
Technical Specifications
16
Power requirements
100-240V, 50/60 Hz or DC, 25 VA
Dielectric
Relay contacts to chassis 1500V rms. for 1 minute
Control terminals to chassis 1500V rms. For 1 minute alarm level
IEC-60255-5
Trip Level Inhibit
25% of systems Ground current
Contact Ratings
DSP-DFM trip contacts-form C SPDT 10 Amp, 240V AC resistive
DSP-DPS Alarm contacts-form C SPDT 8 AMP, 240 V AC resistive
Insulation voltage withstand / lighting impulse withstand in accordance to IEC-60950
Performance
DSP-DFM
Pickup accuracy +/- 10% of system let-through current
Trip Level Accuracy +/- 10A
DSP-DSM
Alarm Level Accuracy +/-10% of IG
Temperature range
Operating temperature 0°C-50°C
MAIN BUS
X0
display and modular design, the DSP
Supply Compartment
OHMNI can be expanded to 50 feeders
for large installations, each with a
G
dedicated feeder module and sensitive
zero - sequence current sensor.
MAIN DISCONNECT
3P
SENTINEL
N
SHUNT TRIP POWER
With its separate easy to read digital
ZSCS
LOADS
PULSE SIGNAL
OHMNI-PM
RESISTOR
TRIP CONTACT
SENSOR INPUT
TRIP CONTACT
A B CNG
SENSOR INPUT
DDR2
SENSOR INPUT
NGR Compartment
LV Compartment
TRIP CONTACT
150VA
RS-485 TO
NETWORK
POWER
AC/DC
DSP-DM
A B CN G
ALARM
CONTACTS
DSP-DPS
DSP-DSM
DSP-DFM
DSP-DFM
DSP-DFM
Features Benefits
DIN-rail parts Compact mounting reduces space requirements
Compact Feeder Modules DSP-DFM
Large systems up to 50 circuits / DSP-OHMNI can be accommodated.
Selectable MUTE ON/OFF function Allows Alarm contact to be used for other applications
Selectable Trip on 1st fault orProvides user the option of maximizing continuity of service (2nd fault
2nd Fault operation
Trip) or minimizing fire/damage risk (1st fault Trip). Both can be used on
the same system.
0-99min Delay setting on 1st Fault Trip
Allows time to locate fault and/or orderly shutdown of equipment.
10-90% Alarm Level setting
User selected Sensitivity in 10% increments, allows maximum sensitivity
to be used while preventing nuisance alarms.
Switching Modules DSP-CAS
Provides co-ordination between systems either vertically (between
zones) or horizontally (same zone) on multi-zone or main-tie-main systems
NGR monitor DSP-DRM Monitors the status of Grounding Resistor in one DSP-OHMNI compatible unit.
Password Protected Setup Four digit codes selectable by user prevent unauthorized setup changes while
still allowing self-test and read-only data.
Self-Test of Modules Internal Self-test of DSP-DFM, DSP-DSM verifies connections to provide
assurance of functionality.
MODBUS Communications llows the operator to remotely monitor which feeder has faulted as well as the
A
leakage currents of all feeders for trending purposes.
CERTIFIED
65287
E232710
17
FUSION
FUSION is a selective coordinated high resistance grounded system
with high first fault current.
Fusion converts from solid grounding to high resistance grounding
giving an immediate reduction in fault current. This allows the fault
to remain on the system without causing further damage and without
unplanned process interruptions.
For faults in minor equipment or smaller feeders it allows the
overcurrent device to trip the circuit and clear the fault and maintains
solid grounding.
Ground faults cause havoc on plant
production processes, shutting down
power and equipment and critical loads.
Ground faults disrupt the flow of
products through manufacturing
processes and cause data loss in
computer centers leading to hours or
even days of lost productivity.
Ground faults pose potential health
and safety risks to personnel, creating
hazards such as equipment malfunctions,
fire and electric shock.
High Resistance Grounding (HRG) is
becoming more prevalent in industrial
and commercial electrical power systems
because it eliminates unscheduled
downtime due to ground faults, and
improves personnel safety by preventing
ground faults from escalating into arcflash incidents. Resistance Grounding
is highly recommended for generators
to protect them from damage due to
excessive ground fault currents.
18
Patented Hybrid Grounding System
in a single enclosure
Current limiting device can be coordinated with
down stream devices to select load to trip
Converts to high resistance grounding to maintain
service continuity at user selected fault levels
Available with integral pulsing capability
for easier fault location
Neutral grounding systems are similar
to fuses in that they do nothing until
something in the system goes wrong.
Then, like fuses, they protect personnel
and equipment from damage. Damage
comes from two factors; how long the
fault lasts and how large the fault is.
The Fusion protects against both
factors, with the grounding resistor
limiting the magnitude of the fault, and
the current limiting device built into the
Fusion, limiting how long the fault lasts
before converting to high resistance
grounding.
The Fusion contains both a current
1. Current Limiting Device
limiting device, a high resistance
A circuit protective device such as a current limiting fuse or circuit breaker
provides a low impedance ground path for the ground fault current to flow.
grounding resistor, a ground fault
sensing relay and is available with
pulsing circuitry.
Time current coordination and selectivity is maintained when the time
current characteristics of the circuit protection device in Fusion is designed
to coordinate with existing over current devices. This ensures that the
over current or ground fault device closest to the load trips and isolates the
faulty equipment.
2. High Resistance Grounding Resistors
This resistor is connected to the wye point of the transformer or
generator supplying the facility. Its function is to limit ground fault currents
to non-damaging levels under a single line-to-ground fault condition.
This provides the user with an opportunity to retain process continuity and
to detect and clear the fault.
3. Automatic Pulsing System (Optional)
Once the pulsing feature on the FUSION system is selected and activated,
the system will cyclically limit the fault to 100%, 75% and 50% of the
available ground fault current. The cyclical pulsing combined with the
hand held pulse tracing sensor empowers the user to trace the fault circuit
to the point of the fault even in complex distribution systems without
de-energizing the load.
4. Ground Fault Sensing Transformer and Relay
This microprocessor based digital relay measures ground fault current
using a 1:1 zero sequence current transformer. It maintains accuracy
over a range of 45Hz to 65Hz and filters out harmonics to eliminate
nuisance tripping.
65287
E222372
19
the power to protect
20
Comparative Performance Rating
For Various Conditions Using
Different Grounding Methods
Method of Grounding
Condition or
Characteristic
Ungrounded
Solid Ground
Low Resistance High Resistance
Immunity to Transient
Overvoltages
Worst
Good
Good
Best
Ground Fault Protection
Can Be Added Easily
Worst
Good
Better
Best
Equipment Protected
Against Arc Fault Damage
Worst
Poor
Better
Best
Safety to Personnel
Worst
Better
Good
Best
Service Reliability
Worst
Good
Better
Best
Maintenance Cost
Worst
Good
Better
Best
Continued Production
After First Ground Fault
Better
Poor
Poor
Best
Ease of Locating
First Ground Fault
Worst
Good
Better
Best
Relay Co-ordination
Not Possible
Good
Better
Best
73% Increase in Voltage
Stress Under Line-To-Ground
Fault Conditions
Poor
Best
Good
Poor
Two Voltage Levels
on the Same System
Not Possible
Best
Not Possible
Not Possible
Reduction in
Frequency of Faults
Worst
Better
Good
Best
First High Ground
Fault Current Flows
Over Grounding Circuit
Worst
Better
Good
Best
Potential Flashover
To Ground
Poor
Worst
Good
Best
the power to protect
how to get in touch
Head Office (Mississauga)
Quebec Office
Western Canada and USA
7615 Kimbel Street, Unit 1
Mississauga, Ontario,
Canada L5S 1A8
P.O. Box 28,
St-Hubert, Québec,
Canada J3Y 5S9
731 Woodpark Road SW
Calgary, Alberta
Canada T2W 2S3
Toll Free 1.888.737.4787
Phone
905.673.1553
Fax
905.673.8472
Toll Free 1.886.441.6464
Phone
450.443.6464
Fax
450.443.6477
Phone 403.255.3855
Cell
403.837.8114
For all International Contacts please visit
www.i-gard.com/contact_int.htm
manuals and guides
C-101 StopLight
C-102 Gemini
C-105 Fusion
High Resistance Grounding
System Manual
High Resistance Grounding
System Manual
Ground Fault Protection
System Manual
C-107 Sentinel
C-408 Sleuth
High Resistance Grounding
System Manual
High Resistance Grounding
System Manual
Ground Fault Protection
on Ungrounded and
High Resistance
Grounded Systems
Application Guide
www.i-gard.com